# Phase transition of Al-hydroxides during the alkaline dissolution of aluminum and their effect on $$^{99} {\text{MoO}}_{4}^{2 - }$$ 99 MoO 4 2 - adsorption behavior

Phase transition of Al-hydroxides during the alkaline dissolution of aluminum and their effect on... The metastable isotope 99mTc is one of the most useful radioisotopes, widely used for nuclear imaging, diagnosis, and therapy. 99mTc is derived from its mother isotope, 99Mo, by alkaline dissolution of neutron-irradiated UAlx targets with Al cladding. For the effective separation of 99Mo from the solution, the formation of Al-hydroxides should be avoided during the dissolution process because Al-hydroxides remove $$^{99} {\text{MoO}}_{4}^{2 - }$$ 99 MoO 4 2 - ions by selectively adsorbing them from the solution. In this study, various conditions for the formation of Al-hydroxides were investigated from the alkaline digest of an Al6061 fake target. Controlled formation of two different phases of Al-hydroxides, gibbsite and bayerite, under different NaNO3/NaOH molar ratios in the dissolution solution was observed. In the solution of 4NaNO3·3NaOH, the gibbsite phase was more dominant than the bayerite phase. On the other hand, the bayerite phase was more favored in the 2NaNO3·1.5NaOH solution. The reaction time also affected the phase transition of the Al-hydroxides. With an increased reaction time, the formation of the bayerite was more promoted than the gibbsite. Additionally, the adsorption of $$^{99} {\text{MoO}}_{4}^{2 - }$$ 99 MoO 4 2 - ions on both gibbsite and bayerite was characterized using ICP-AES. One gram of bayerite attracted up to 4.8 mg of Mo-ions, and this is significantly larger than the amount adsorbed on the gibbsite. This research focused on the optimal alkaline dissolution conditions to minimize the loss of $$^{99} {\text{MoO}}_{4}^{2 - }$$ 99 MoO 4 2 - during the process. The formation of bayerite should be avoided by controlling the solution concentration, initial temperature, and reaction time. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Research on Chemical Intermediates Springer Journals

# Phase transition of Al-hydroxides during the alkaline dissolution of aluminum and their effect on $$^{99} {\text{MoO}}_{4}^{2 - }$$ 99 MoO 4 2 - adsorption behavior

, Volume 42 (3) – Jul 4, 2015
11 pages

/lp/springer_journal/phase-transition-of-al-hydroxides-during-the-alkaline-dissolution-of-EE6pk0SgjF
Publisher
Springer Netherlands
Subject
Chemistry; Catalysis; Physical Chemistry; Inorganic Chemistry
ISSN
0922-6168
eISSN
1568-5675
D.O.I.
10.1007/s11164-015-2155-6
Publisher site
See Article on Publisher Site

### Abstract

The metastable isotope 99mTc is one of the most useful radioisotopes, widely used for nuclear imaging, diagnosis, and therapy. 99mTc is derived from its mother isotope, 99Mo, by alkaline dissolution of neutron-irradiated UAlx targets with Al cladding. For the effective separation of 99Mo from the solution, the formation of Al-hydroxides should be avoided during the dissolution process because Al-hydroxides remove $$^{99} {\text{MoO}}_{4}^{2 - }$$ 99 MoO 4 2 - ions by selectively adsorbing them from the solution. In this study, various conditions for the formation of Al-hydroxides were investigated from the alkaline digest of an Al6061 fake target. Controlled formation of two different phases of Al-hydroxides, gibbsite and bayerite, under different NaNO3/NaOH molar ratios in the dissolution solution was observed. In the solution of 4NaNO3·3NaOH, the gibbsite phase was more dominant than the bayerite phase. On the other hand, the bayerite phase was more favored in the 2NaNO3·1.5NaOH solution. The reaction time also affected the phase transition of the Al-hydroxides. With an increased reaction time, the formation of the bayerite was more promoted than the gibbsite. Additionally, the adsorption of $$^{99} {\text{MoO}}_{4}^{2 - }$$ 99 MoO 4 2 - ions on both gibbsite and bayerite was characterized using ICP-AES. One gram of bayerite attracted up to 4.8 mg of Mo-ions, and this is significantly larger than the amount adsorbed on the gibbsite. This research focused on the optimal alkaline dissolution conditions to minimize the loss of $$^{99} {\text{MoO}}_{4}^{2 - }$$ 99 MoO 4 2 - during the process. The formation of bayerite should be avoided by controlling the solution concentration, initial temperature, and reaction time.

### Journal

Research on Chemical IntermediatesSpringer Journals

Published: Jul 4, 2015

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